This invention relates generally to the field of building blocks, usually formed of cementitious material, which are used as stacked components in the construction of walls and structures. More particularly, the invention relates to such articles which are shaped such that the blocks interlock or align when stacked.
Cementitious building blocks, often known as cement or concrete blocks, are well known in the masonry and construction fields. In the most common configuration, the blocks are rectangular with dimensions of approximately 8 inches in height and depth and 16 inches in length. The blocks are not solid but are provided with two vertically oriented openings separated by a lateral internal wall or web member, such that the blocks possess a shape similar to the number "8" with rectangular corners when viewed from the top or bottom. The open interiors reduce the weight of the block, allow less material to be consumed in their formation, and provide vertical channels in the finished wall structure for the passage of wiring, plumbing or conduits, or for receipt of filler materials such as poured concrete to increase strength, insulation or other properties. Such blocks have been in use for many years, and when properly joined by mortar interspersed between adjacent blocks they form extremely solid structures. Constructing a wall from discrete blocks requires a certain degree of skill, since wet mortar must be applied to the proper surfaces of the previously laid blocks and/or to the proper surfaces of the block to be laid, then the block must be positioned and aligned with the previously laid blocks such that the height of each row remains constant and such that the wall possesses a planar inner and outer surface.
Because the proper laying of block is a time-consuming, labor-intensive and skilled task, alternative block structures, configurations and systems have been developed which address one or more of these problems. One approach has been to provide mortarless blocks, i.e., blocks which interlock in a secure manner without the need for the addition of mortar or other bonding material between individual blocks. The blocks are usually constructed such that each possesses both male and female mating components, such as a pair of longitudinal channels on the top and a pair of longitudinal ridges on the bottom, so that the channels of the lower block receive the ridges of the block set above it. Other projection/recess or tongue/groove mating configurations are also known and utilized. Many systems use the interlocking blocks merely as forms to receive poured concrete, with the blocks often formed of polystyrene foam. Examples of such systems are seen in U.S. Pat. No. 5,901,520 to Abdul-Baki, U.S. Pat. No. 5,894,702 to Stenekes, U.S. Pat. No. 5,623,797 to Gravier et al., U.S. Pat. No. 5,457,926 to Jensen, U.S. Pat. No. 4,186,540 to Mullins, and U.S. Pat. No. 3,534,518 to Zagray. Mortarless systems have met with rather limited success, however, since conventional block-making equipment cannot produce blocks with less than a 1/16 inch variation in height between individual blocks. Even such a small variation is enough to cause unacceptable deviation from plumb after only 3 or 4 courses. The use of mortar between blocks compensates for this variation, since the height of the mortar can be varied to properly position each block at the proper height. Mortar also serves to seal joints and provides a measure of flexural strength, so eliminating mortar is not necessarily beneficial.
Other systems of interlocking or aligning blocks have been developed where mortar or grout is still used in some degree to join adjacent blocks in a more secure manner beyond that provided by the interlocking or aligning structures alone. For example, Brooke in U.S. Pat. No. 800,067 discloses blocks having longitudinal tongue and groove alignment means along the edges, where mention is made that cement or grout is utilized to construct the wall. Buyer in U.S. Pat. No. 2,019,653 shows blocks having centralized raised bosses and corresponding sockets for alignment, where the bosses sockets have a flat surface bounded by two sloping lateral surfaces, where the flat and sloping surfaces abut directly when the blocks are stacked. A recess is provided along the horizontal joint between courses for receiving mortar or grout after the blocks have been stacked. Finally, Huag et al. in U.S. Pat. No. 4,787,189 shows another type of interlocking blocks where the center of the blocks have longitudinal tongue and groove configurations. A problem with the Brooke and Huag et al. systems is that both still require skilled application of the mortar in the right amount to the proper locations, since there is no provision in the designs to allow for excess or misplaced mortar. Any mortar which inadvertently falls into the tongue and groove areas will interfere with and prevent proper alignment of the blocks, necessitating the lifting of the block and removal of the excess material. The Buyer system is in effect a mortarless system, with all the inherent problems of those types, since the mortar or grout is not applied until after the blocks have been stacked. Should the mortar be applied prior to stacking, the Buyer design likewise provides no margin for application error, since the sloped surfaces make direct contact when the blocks are stacked and excessive or misplaced mortar will interfere with the proper fit and alignment.
It is an object of this invention to provide a cementitious building block and system where the blocks are self-aligning and interlock to provide a wall structure having generally planar inner and outer wall surfaces, where the courses are easily maintained at plumb as the height of the wall increases. It is a further object to provide such a block and system where the blocks can be properly stacked in a fast and non-complicated manner, such that the task can be performed by relatively unskilled labor having only the most basic of mortar application skills. It is a further object to provide such a system where mortar is utilized to join adjacent blocks, such that the joints are sealed, flexural strength is enhanced, and variations in block height can be compensated for. These and other objects not expressly stated will be apparent based on the disclosure and description of the invention, its best mode and preferred embodiment, as set forth below.